I have shot quite a few HST's in a few different calibers and did my own backyard personal testing Nothing real technical. One thing I did find is that even firing into soft rotted wood from 7-10 yds., they will expand. Not 100% but I would say 7 out of 10 on average. It's my go to carry ammo besides Win. Silvertip. So, I do think that some HST's could expand going through fiberglass. JMO.........................Just in case someone wants to take that Vette shot..........................